solve_game() is passed the _initial_ game state, not the most recent

solve_game() is passed the _initial_ game state, not the most recent
one; so we can't just set `ret->completed = ret->movecount' and hope
it's been set to something other than zero. Instead, we set both
move counts to 1, which is entirely arbitrary but works.

This fixes a subtle bug with the Solve feature: if you pressed
Solve, then disturbed the grid, then brought it back to the solved
state by making more forward moves (rather than using Undo), then
the first time you did this the `Moves since auto-solve' status line
would reset to zero.

[originally from svn r5759]